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Brief Summary

    Oregon spotted frog: Brief Summary
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     src= Recently hatched R. pretiosa larvae near Olympia, WA.

    The Oregon spotted frog (Rana pretiosa, meaning "precious frog") is a member of the frog family Ranidae of order Anura. It is a medium-sized aquatic frog endemic to the Pacific Northwest and historically well distributed in the Puget Trough/Willamette Valley province and the Cascade Mountains of south-central Washington and Oregon. It is relatively rare within its range and is listed globally as vulnerable.

Comprehensive Description

    Description
    provided by AmphibiaWeb text

    This robust frog may be brown, reddish-brown or red above with a variable number of large, black spots and blotches on the back, sides, and legs. The spots are usually irregular-shaped, with indistinct edges and light centers. The skin on back and sides is often covered with small bumps and tubercles. The eyes are upturned. The lower abdomen and the undersides of the hind legs are usually colored by a reddish-orange or salmon-colored pigment that appears as though it has been painted on (Leonard et al. 1993; Nussbaum 1984; Stebbins 1985). Oregon spotted frogs have relatively short hind legs and extensive webbing between the toes of the hind feet. Sexually mature females range between 60 and 100 mm snout-vent length and males range between 45 and 75 mm (Licht 1975).

    Since nearly the time of its original description in 1853, the systematics of the "Western Spotted Frog" group has been a source of both confusion and debate. In 1996, however, a team led by David M. Green published the results of a study on the genetics of Spotted Frogs and concluded that the group actually contained two "sibling" species-the Oregon Spotted Frog and the Columbia Spotted Frog (Green et al. 1996 1997) . The decision to "split" the species was based upon the results of laboratory studies that indicated significant genetic differences, despite a lack of reliable morphological differences. Because the two species have allopatric ranges, they may be reliably identified based upon the location where a frog is encountered.

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    Oregon spotted frog
    provided by wikipedia

     src=
    Recently hatched R. pretiosa larvae near Olympia, WA.

    The Oregon spotted frog (Rana pretiosa, meaning "precious frog") is a member of the frog family Ranidae of order Anura. It is a medium-sized aquatic frog endemic to the Pacific Northwest and historically well distributed in the Puget Trough/Willamette Valley province and the Cascade Mountains of south-central Washington and Oregon.[4][5] It is relatively rare within its range and is listed globally as vulnerable.[1]

    Distribution

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    The range of the Oregon spotted frog (in Oregon, USA).

    Oregon spotted frogs can be found in south-western British Columbia, Canada, south through the Puget/Willamette Valley through and the Columbia River gorge in south-central Washington to the Cascade Range at least to the Klamath Valley in Oregon, USA.[1] They were previously found in California but have been extirpated there[6] and have also been extirpated from much of western Oregon and Washington. They can occur at an elevation of 20-1,570m asl.[1]

    In Oregon, the Oregon spotted frog's current range is Deschutes, Lane and Klamath counties.[7] In Washington, Oregon spotted frogs occur in Thurston County.[4]

    Description

    As adults, the Oregon spotted frogs can range from about 4.4–10.2 cm (1.75–4 in) in snout-vent length which is the distance from the snout of the frog to the hide end/vent of the frog. Similar to most amphibians, the females tend to be larger than the males for reproductive reasons. The coloration of this species varies with age.[4] As tadpoles, their back and tail musculature are brown and lack dark spotting, while the belly is a creamy white or aluminum color.[8] Juveniles are usually some shade of brown, but may sometimes be olive green. Adult Oregon spotted frogs can be brown or reddish brown and tend to become increasingly red with age.[4] Both juvenile and adult Oregon spotted frogs have black spots with light centers present on their heads and backs which tend to become larger, darker and get an increasingly ragged-edged appearance with age. Older frogs also tend to become brick red over most of their dorsal surfaces and are frequently red on their entire abdomen forward to their chest.[4] Juveniles are white or cream in color with reddish pigments on their underlegs and abdomen while adults show a vivid orange-red color on their underlegs and red surface pigments on their abdomen. The dorsal lateral folds tend to be lighter in color ranging from tan to orange.[4] The hind legs of the Oregon spotted frog are short relative to its body length and their groin tends to be uniformly gray but can sometimes be faintly mottled with gray markings and red-orange flecks. Their hind feet are fully webbed and the webbing normally extends onto the last segment of the longest toe. The Oregon spotted frog has eyes that are upturned and mostly uncovered by the eyelids when viewed from above.[8]

    Habitat

    The Oregon spotted frog is a highly aquatic frog that seldom strays from areas of standing water. Bodies of water (i.e., wetlands, lakes and slow-moving streams) that included zones of shallow water with abundant emergent or floating aquatic plants are suitable for the Oregon spotted frogs. Mats of aquatic vegetation are used for basking on and escaping danger by diving beneath the cover of the vegetation. These habitats often provide a thin layer of unusually warm water which the frogs appear to prefer.[4]

    Diet

    Adult Oregon spotted frogs feed on a variety of live animal prey, including mostly insects, while Oregon spotted frog tadpoles feed on algae, rotting vegetation, and detritus.[4]

    Reproduction

    The Oregon spotted frog’s reproduction is strictly aquatic and their late winter breeding season is brief, less than four weeks in duration. Males call quietly during the day or night from the vicinity of traditional oviposition sites, places where females lay their eggs in communal piles.[4] Ovipostition at selected sites is initiated when water temperatures reach 8 °C, but the timing of oviposition varies from late February-early March at lowland sites to late May-late June at montane sites in Oregon.[9] They breed in warm shallow water, often 5.1–30.5 cm (2–12 in) deep in areas where grasses, sedges, and rushes are usually present. Adult females reportedly breed every year and probably produce a single egg mass each year. Though egg masses are occasionally laid singly, communal oviposition sites usually comprise the majority of the annual reproductive output. These communal clusters of egg masses are often composed of between 10 and 75 individual egg masses and in British Columbia it has been recorded that each egg mass contained an average of 643 eggs. They lay their eggs in fully exposed, shallow waters that are readily warmed by the sun so that development to hatching is hastened by warm conditions. However this also increases the vulnerability of the eggs to desiccation and/or freezing.[4]

    Lifecycle

    Once fertilized, the eggs of the Oregon spotted frog begin to enter the larval stage of their development very quickly. The larvae then hatch into tadpoles in 18–30 days and do not metamorphosize until 110–130 days after hatching in British Columbia, and potentially as short as 95 days in Oregon. After the transformation from a tadpole into a juvenile frog, the juveniles may remain around the breeding ponds for a period of time, although their emigration patterns are unknown. Once the Oregon spotted frog has reached adulthood, in British Columbia the males can become sexually mature within their second year and females are thought to become sexually mature in either their second or third year. In central Washington on the other hand, most males are sexually mature by the end of their first year and females become sexually mature by the middle of their second year. The longevity of the Oregon spotted frog is not well studied, but it is thought that these frogs have a relatively short life, generally living between two and five years.[9]

    Subspecies

    Columbia spotted frog Rana pretiosa luteiventris (Thompson, 1913) was initially described as subspecies of Rana pretiosa but has since been elevated to full species status.[10]

    Conservation status

    The Oregon spotted frog is listed internationally on the IUCN Red List as vulnerable.[1] It is a candidate for listing in the United States[11] under the Endangered Species Act, and it is listed as endangered in Canada[12] under the Species At Risk Act. Its decline has also been linked to areas inhabited by the introduced bullfrog and related to loss and degradation of breeding habitat such as may result from dam construction, alteration of drainage patterns, dewatering due to urban and agricultural use of water, excessive livestock grazing, and other human activities that reduce or eliminate lentic shallow water.[1]

    Recovery program

    Several organizations associated with the NW Zoo and Aquarium Alliance[13] are working on recovery projects for the Oregon spotted frog.[6] These include the Vancouver Aquarium,[14] the Greater Vancouver Zoo,[15] the Woodland Park Zoo,[16] the Washington State Department of Fish and Wildlife,[17] Northwest Trek Wildlife Park, and Evergreen State College.[18] School groups are also involved in enhancing habitat for the Oregon spotted frog by managing canarygrass and bullfrogs. Education of naturalists resulted in detection of new sites.[19]

    See also

    References

    1. ^ a b c d e f Hammerson, G & Pearl, C. (2004). "Rana pretiosa". The IUCN Red List of Threatened Species. IUCN. 2004: e.T19179A8848383. doi:10.2305/IUCN.UK.2004.RLTS.T19179A8848383.en. Retrieved 10 January 2018..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
    2. ^ IUCN (International Union for Conservation of Nature), Conservation International & NatureServe. 2004. Rana pretiosa. In: IUCN 2014. The IUCN Red List of Threatened Species. Version 2014.3. http://www.iucnredlist.org. Downloaded on 01 June 2015.
    3. ^ National Geophysical Data Center, 1999. Global Land One-kilometer Base Elevation (GLOBE) v.1. Hastings, D. and P.K. Dunbar. National Geophysical Data Center, NOAA. doi:10.7289/V52R3PMS [access date: 2015-03-16].
    4. ^ a b c d e f g h i j Kelly R. McAllister & William P. Leonard (July 1997). "Washington State Status Report for the Oregon Spotted Frog". Washington Department of Fish and Wildlife. Retrieved 9 September 2012.
    5. ^ Frost, Darrel R. (2014). "Rana pretiosa Baird and Girard, 1853". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 31 January 2015.
    6. ^ a b "NW Zoo and Aquariaum Alliance Species Recovery Projects".
    7. ^ "Endangered Species Fact Sheet: Oregon spotted frog". U.S. Fish and Wildlife Service. Retrieved 2007-10-01.
    8. ^ a b Leonard, William P. (1993). Amphibians of Washington and Oregon (third ed.). Seattle Audubon Society.
    9. ^ a b "Rana pretiosa: Oregon Spotted Frog".
    10. ^ Frost, Darrel R. (2014). "Rana luteiventris Thompson, 1913". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 31 January 2015.
    11. ^ "Species Fact Sheet: Oregon spotted frog, Rana pretiosa". U.S. Fish & Wildlife Service. Retrieved March 6, 2013.
    12. ^ "COSEWIC Assessment and Status Report on the Oregon Spotted Frog Rana pretiosa in Canada" (PDF). Committee on the Status of Endangered Species in Canada. Retrieved March 6, 2013.
    13. ^ "The NW Zoo & Aquarium Alliance".
    14. ^ "Vancouver Aquarium recovery project".
    15. ^ "Greater Vancouver Zoo recovery project". Archived from the original on 13 May 2008.
    16. ^ "Frog recovery program making headlines".
    17. ^ "Oregon spotted frog released into the wild to halt population crash".
    18. ^ Sullivan, Jennifer (2009-07-06). "Researchers stunned by inmates' success raising endangered frogs". The Seattle Times.
    19. ^ Dodge, John (2011-09-30). "Students aid endangered spotted frog. Wetlands: Program aims to boost numbers of Oregon spotted frog". The Olympian.

Distribution

    Distribution and Habitat
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    The Oregon spotted frog once occurred from southwest British Columbia through western Washington and Oregon into northeastern California. Today the species is known from three localities in British Columbia, four localities in Washington and approximately twenty-four localities in Oregon (Marc Hayes pers. comm.) (McAllister and Leonard 1997; Green et al. 1997). In Washington, it occurs at elevations ranging from 40 to 620 meters (McAllister and Leonard 1997) .

    Oregon spotted frog populations occur in association with relatively large wetland complexes. Breeding occurs in shallow, relatively unshaded emergent wetlands. The breeding ponds, which are typically dry by mid- to late summer, range in depth from 2 to 14 inches during the breeding season, and are vegetated by low-growing emergent species such as grasses, sedges (Carex spp.), and rushes (Juncus spp.). After breeding adults disperse into adjacent wetland and riparian habitats. Adults remain active year-around near sea-level, but freezing temperatures apparently cause adults and juveniles to hibernate in streams, oxbows and springs at higher elevations.

Trends

    Life History, Abundance, Activity, and Special Behaviors
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    Breeding occurs sometime in February or March at lower elevations, but does not occur until March or April at the two Washington sites in the Cascade Range (McAllister and Leonard 1997). The Oregon Spotted Frog exhibits strong fidelity to breeding sites and eggs are often deposited the same locations in successive years.

    Males arrive first, gathering in "lek-like" groups and float in the shallows, calling while awaiting the arrival of a female. Male advertisement calls, consisting of a rapid series of 5 to 50 faint "tapping" notes notes, are given throughout the breeding season (particularly on sunny days) and again in fall (Davidson 1995; Leonard et al. 1997). Most breeding takes place within a two-to-three-week "window" when most of eggs are deposited. However, breeding may be interrupted for up to several weeks by the onset of cold weather; in such cases a second bout of breeding may occur. Upon release, the ova are tightly packed in a mass roughly the size of a ping-pong ball, but within a few hours the mass swells to the size of an average-size human fist. Females usually lay their eggs atop or adjacent to other egg masses (some of the larger aggregations may contain more than 100 individual egg masses). The egg masses are not attached to vegetation, but are deposited in still, shallow waters atop submergent herbaceous vegetation or freely floating amongst clumps of emergent wetland plants such as sedges (Carex spp.) and rushes (Juncus spp). Often-times, the the upper portions of the egg masses protrude above the water surface resulting in severe egg mortality from freeze-thaw damage or desiccation.

    After a few weeks of embryonic development, thousands of small tadpoles emerge and cling to the remnants of the gelatinous egg masses, their densely packed, dark bodies acting as solar collectors and warming the water adjacent to the mass. After several days, the hatchlings become free-swimming tadpoles, using their minute brush-like mouthparts to feed upon algae, detritus, and, in some cases, bacteria (but see McDiarmid and Altig 1999). Tadpoles may grow to 90 mm total length before metamorphosing in their first summer or fall (Licht 1975) .

    Mortality of eggs, tadpoles, and newly metamorphosed frogs is high, and it is likely that only about 1% of an annual cohort survive to the first winter (Licht 1974) . Near sea-level sexual maturity is attained at age two, while at higher elevations one or two additional years is required (Licht 1975).

    Adults feed upon arthropods (e.g., spiders, insects), earthworms and other invertebrate prey. In turn, Oregon Spotted Frogs may be preyed upon by mink, river otter, raccoon, herons, bitterns, corvids and garter snakes (Licht 1974) , while larvae may be consumed by larvae of dragonflies, predacious diving beetles, fish, garter snakes and wading birds.

Threats

    Life History, Abundance, Activity, and Special Behaviors
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    This species is rare and has undergone significant declines in range over the past half century. It is now presumed to be extirpated in California and is in serious jeopardy in southwestern British Columbia, Canada. The most probable cause for this frog's precipitous decline is the hydrological modification and destruction (draining, flooding, and filling) of specialized shallow-water, emergent wetlands used for breeding. However, introduced predators including bullfrogs and sport fishes pose serious threats from predation and from competition for critical habitats.